In dynamoelectric machines such as small fractional-horsepower motors, the armature shaft is supported by antifriction bearings mounted within recesses or bearing seats in the opposite endcaps of the motor housing. Various techniques have been utilized to retain the bearing in the recess. Some of the common techniques include press-fit mounting, adhesives and various mechanical means to capture the bearing in place. In some instances, a combination of two or more techniques may be utilized.
Such techniques are generally not satisfactory in applications where the motor is subjected to severe axial loading and/or impact. For example, electric windshield wiper motors generally experience severe axial loading and/or impact which tends to hammer the bearing out of the bearing seat. In a typical windshield wiper motor configuration, the motor armature drives a worm gear through a worm on the armature shaft. In turn, the worm gear drives a shaft with a crank arm. Various types of linkage interconnect the crank arm to another crank arm which is in turn connected to the windshield wiper arms. As the armature rotates, the crank arm on the worm gear converts the rotary motion of the worm gear to a reciprocating motion that is transmitted to the windshield wiper arms. As the wiper arms reach the end of travel across the windshield, inertia, together with the sudden reversal of direction, transmits high loading back through the linkages to the gear. This high loading is in turn transmitted to the motor armature shaft. The armature shaft thrusts axially on the bearing in such a direction as to tend to force the bearing out of its seat. Consequently, the bearing retaining means must be sufficient to retain the bearing during severe axial loading in order to prevent dislodgement of the bearing and a breakdown of the motor.